1. Field of the Invention
The present invention relates to apparatus for continuously coating the surface of a traveling web with a liquid preparation. More particularly, the present invention relates to an apparatus for coating an indefinite length liner web while in transit through a corrugated paperboard fabricating machine.
2. Description of the Prior Art
Corrugated paperboard is normally fabricated from reeled paper web supplies of indefinite length by a series of forming and laminating steps. The corrugated medium is formed first in the meshing nip of two fluted surface cylinders. Prior to release from the second cylinder flutes, tips of the medium web formed thereto are adhesively secured to the face of a first paper liner web to secure the periodic distance between adjacent flute tips. Assembly completion of a double-faced board product comprises the adhesive lamination of a second liner web to the exposed side flute tips of a previously assembled single-face product.
Countless permutations of the above process are possible to achieve a desired performance specification or esthetic appearance.
For normally stocked box applications, the liner web faces of the laminated assembly are fabricated of 0.009 to 0.030 inch caliper unbleached kraft process paper. Particular customers, however, have the outer liner face of their boxboard containers coated for improvement of the print surface quality, it being their objective to provide advertising or content information directly on the container surface. Such coating and printing must be applied prior to the corrugated assembly due to the incompatibility of the resilient corrugated board section with rotary printing machines. Consequently, box manufacture order lots of coated or printed faces boxes are usually handled individually and require stoppage of the corrugating machinery for material changes and machinery adjustment. This machine downtime represents unproductive capital and thereby dramatically increases the production cost of each coated surface box order.
Within the scope of specially ordered boxboard products are those which are merely coated but not printed. In this case, the liner coating may be applied at the "double-facer" station to normal liner web stocks without other changes in the corrugating machine operation. Unfortunately, prior art machine applied face coatings of boxboard liner web stock have been crude and tend to produce a product of inferior quality. Usually, these coating defects are directly attributable to poor design practices and the fact that prior coating devices use stationary wiper blades for spread and distribution control.
It is therefore, an object of the present invention to provide a web coating apparatus that is capable of first quality productivity and is removable from the double-facer machine proximity when not in use.
Another object of the present invention is to provide a portable gravure roll coating apparatus.
Another object of the present invention is to provide a gravure roll coating apparatus having a counter-rotating wiper roll to even the coating film thickness over the gravure roll surface.
Another object of the present invention is to provide a portable, gravure roll, web coating apparatus that is primarily powered by the traveling web coat subject.